Effects of capsaicin on myenteric neurons of the guinea pig ileum.

The effects of capsaicin on the electrophysiological behavior of myenteric neurons were investigated with intracellular recording techniques in the isolated guinea pig ileum. Capsaicin evoked a marked long-lasting slow depolarization associated with increased input resistance, during which the cells spiked repeatedly or displayed anodal break excitation. Capsaicin did not produce the slow depolarizing action on myenteric neurons in Ca2(+)-free media (with 0.1 mM ethylenediaminetetraacetic acid) or in the mesenteric denervated ileum. This action of capsaicin on myenteric neurons seems to be mediated via a release of substance P, possibly from sensory nerve endings.